1. Field of the Invention
The present invention relates to carrying cases and, more particularly, to a unique sealed assembly of parts forming a watertight insulated carrying case.
2. Description of the Prior Art
The construction of soft-sided or semi-rigid carrying cases has been a labor intensive high-cost process. Sewing watertight seams for interior and exterior corners is difficult and requires much care and skill. Close monitoring of quality and conducting seam testing procedures result in additional costs.
To alleviate some of the above problems, heat sealing techniques evolved. Instead of gluing or sewing, adjoining edges of heat sealable plastics were fused together by heat or electromagnetic energy to form a watertight joint. This worked good for plastic layers being joined from one or two dimensions. Great difficulty was encountered, however, when three dimensional corner joints were connected and fused together. Plastic fold lines occurred allowing water leaks. Conplicated heating dies and fixtures were also required.
The problem was aggravated when multiple layers of plastic were being joined and/or when the plastic was covering irregular three dimensional structure. Further problems occurred when the structure itself was resilient.
All of the above frequently resulted in misalignment and missed edges during the heat fusing process. As a result, the seams would come apart and the entire case would have to be reconstructed. Missed interior seams were difficult to detect by quality control monitors. This, of course, resulted in sales of a defective product and subsequent consumer dissatisfaction.